The present invention generally relates to a low drop-out voltage regulator (LDO) and, more particularly, to an LDO with a charge pump circuit and an auxiliary startup circuit, and a method for starting the LDO.
Charge pump circuits are often used to generate a higher voltage output from a lower voltage input. A Low drop-out voltage regulator (LDO) converts and regulates an input voltage so that a receiving circuit receives an expected voltage value. For example, if a system requires a steady 5V input, a charge pump may be used to pump 3V to 6V and then a LDO is used to regulate the 6V charge pump output to provide the required 5V system input.
Systems with multiple voltage domains have become increasingly common in integrated circuits, so it is possible that a LDO will be connected to multiple supply voltages and multiple input voltages, and generate multiple regulated voltages. However, when there are multiple supply voltages, the LDO output voltage may drop to a level that is too low to drive the charge pump. Accordingly, it would be advantageous to have a LDO that can operate correctly even when its output voltage is too low to drive a charge pump.